BUG: Deadlock while cache eviction

[apoorvyadav1111]

Hi team,

This issue was first reported as per conversation on the discord community by Ritik. To replicate the issue, please follow the steps below:

1. Update the KeysLimit in dice/config/config.go var KeysLimit int = 2 // default buffer size.
2. Run following commands mset a b c d works fine set x y should lead to deadlock

Upon initial debugging, I found the issue is due to the locks being acquired in functions when trying to set a new value. Please find the sequence leading to deadlock below:

1. evalSet calls store.Put()
2. store.Put() calls PutHelper with acquiring Lock()
3. PutHelper() validates the key limit and goes for eviction via store.evict()
4. In populateEvictionPool() we try to get RLock() to evict, which causes deadlock as Lock() is already acquired on step 2.

cc: @JyotinderSingh

Regards, Apoorv